使用Zookeeper实现分布式锁的最佳实践

news2024/10/6 2:09:53

使用Zookeeper实现分布式锁的最佳实践

大家好，我是微赚淘客系统3.0的小编，也是冬天不穿秋裤，天冷也要风度的程序猿！

1. 引言

在分布式系统中，保证资源的安全访问是一项关键任务。分布式锁作为实现这一目标的重要工具，能够有效地控制不同节点对共享资源的访问。本文将深入探讨如何利用Zookeeper实现分布式锁，包括实现细节、代码示例以及注意事项。

2. Zookeeper简介

Zookeeper是一个开源的分布式协调服务，提供了高可用、高性能的分布式锁机制。它通过在集群中的多个节点之间共享数据来实现分布式锁的管理，确保只有一个节点能够获取到锁。

3. 实现分布式锁的步骤

在Java语言中，我们可以通过Zookeeper的临时顺序节点和Watcher机制来实现分布式锁。下面是一个简单的示例代码，演示如何使用Zookeeper实现一个分布式锁：

package cn.juwatech.distributedlock;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;

public class DistributedLockExample {

    private static final String ZOOKEEPER_CONNECTION_STRING = "localhost:2181";
    private static final int SESSION_TIMEOUT = 5000;
    private static final String LOCK_PATH = "/distributed_lock";

    private ZooKeeper zooKeeper;
    private String currentZnodeName;

    public DistributedLockExample() throws IOException {
        this.zooKeeper = new ZooKeeper(ZOOKEEPER_CONNECTION_STRING, SESSION_TIMEOUT, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // Watcher实现
            }
        });
    }

    public void acquireLock() throws KeeperException, InterruptedException {
        while (true) {
            createLockNode();
            List<String> children = zooKeeper.getChildren(LOCK_PATH, false);
            Collections.sort(children);
            String smallestNode = children.get(0);
            if (currentZnodeName.equals(LOCK_PATH + "/" + smallestNode)) {
                return;
            } else {
                waitForLock(children.get(Collections.binarySearch(children, currentZnodeName.substring(LOCK_PATH.length() + 1)) - 1));
            }
        }
    }

    private void createLockNode() throws KeeperException, InterruptedException {
        Stat stat = zooKeeper.exists(LOCK_PATH, false);
        if (stat == null) {
            zooKeeper.create(LOCK_PATH, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }
        currentZnodeName = zooKeeper.create(LOCK_PATH + "/", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
    }

    private void waitForLock(String prevZnodeName) throws KeeperException, InterruptedException {
        CountDownLatch latch = new CountDownLatch(1);
        Stat stat = zooKeeper.exists(LOCK_PATH + "/" + prevZnodeName, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                if (event.getType() == Event.EventType.NodeDeleted) {
                    latch.countDown();
                }
            }
        });

        if (stat != null) {
            latch.await();
        }
    }

    public void releaseLock() throws KeeperException, InterruptedException {
        zooKeeper.delete(currentZnodeName, -1);
        zooKeeper.close();
    }

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        DistributedLockExample lockExample = new DistributedLockExample();
        lockExample.acquireLock();

        // 执行需要加锁的业务逻辑

        lockExample.releaseLock();
    }
}

4. 实现细节解析

在上述代码中，我们首先连接到Zookeeper服务器，并创建一个名为/distributed_lock的持久化节点作为锁的根节点。接着，通过创建临时顺序节点来竞争锁，使用Zookeeper的节点顺序特性来确定锁的持有者。如果当前节点的序号是最小的，则获取到锁；否则，通过Watcher监听前一个节点的删除事件，实现等待锁释放。

5. 注意事项